The present invention relates to a vacuum drying apparatus and a vacuum drying method, and more particularly, to a vacuum drying apparatus and a vacuum drying method in which a time required for drying can be reduced, and a drying surface of an object to be dried is satisfactory.
In the case of a color filter for an LCD, for example, a glass substrate is applied with coating liquid such as resist liquid and dried to form a desired pattern by such a photolithography or the like. As coating liquid application system, for example, a spin coating system, a knife coating system, a roll coating system, a bead coating system, or the like can be employed. In any case of application such as mentioned above, a drying process for drying a coating film is required to be taken before a pattern forming process. Conventionally, for an object to be dried such as a glass substrate coated with coating liquid, heat drying has been performed in an oven or a hot plate or the like.
The above method by heating requires long time for drying, and accordingly, in the manufacturing process of a color filter for an LCD as described above, the drying step of the glass substrate coating film has been the rate-determining step for the whole process. Accordingly, in recent years, a vacuum drying apparatus has come to be used so as to make it possible to reduce the time for the drying step. This is a system in which a glass substrate having a coating film is placed in a vacuum state to elevate the solvent evaporation rate to a remarkable extent.
However, even by using such a vacuum drying apparatus, it is invariable that the drying step occupies the rate-determining step for the whole process, and therefore, a further reducing of the time for the drying step is an important subject.
On the other hand, in the manufacturing process of the color filter for an LCD, the requirement is not only the reducing of the drying time but also the smoothness of the surface of the dried coating film on the glass substrate. In case of the drying by a simple rapid pressure reduction, irregularities are formed on the surface of the coating film to make the product not practically usable.